Methods of implanting an intraocular lens

ABSTRACT

The present invention refers to a method of restoring the vision of an eye having an impaired lens with an artificial lens implant. The method involves replacing the lens by a polymerizable material injected into the emptied lens capsule and thereby providing a new lens implant with a predetermined refractive value, while admitting the possibility of controlling and adjusting the refractive value of the eye during the surgical process.

FIELD OF INVENTION

[0001] The present invention refers to a method of restoring vision ofan eye having an impaired lens with an artificial lens implant. Themethod involves replacing the lens by a polymerizable material injectedinto the emptied lens capsule and thereby providing a new lens implantwith a predetermined refractive value, while admitting the possibilityof controlling and adjusting the refractive value of the eye during thesurgical process.

BACKGROUND OF INVENTION

[0002] In the field of ophthalmic cataract surgery, wherein a defectnatural lens is replaced with an artificial lens, there has been adevelopment towards lenses and methods, which inflict less surgicaltrauma. For many years most of the IOLs were made ofpoly(methylmethacrylate) (PMMA), a material with good opticalcharacteristics and compatibility with tissues in the eye. Adisadvantage of PMMA, however, is that it is a very rigid material and asurgical incision must be made large enough, at least 5-6 mm, for theimplantation of the lens. With improved devices for removal of thenatural lens by phacoemulsification, requiring only a rather smallincision, there was a need for lenses with deformable optics, asdisclosed in the U.S. Pat. No. 4,573,998 (Mazzocco). There are presentlyseveral types of foldable intraocular lenses on the market which can beinserted through a considerably smaller incision of about 3 to 4 mm, forexample made from specifically designed silicone materials.

[0003] Even with the mentioned types of improved implantable IOLs, nowavailable on the market, there is still a desire to obtain a lens whichadmits the use of an even smaller incision and behaves like the naturallens in the eye, i.e. will be accommodating with a focal point regulatedby action of the ciliary muscle in the eye. In order to allow for areally small incision it would be necessary to form the lens inside theeye from a solution which is injected into the capsular bag or into aballoon placed inside the bag by means of a standard injection needle.

[0004] IOLs formed from an injected solution of a silicone prepolymer,crosslinker and catalyst have already been suggested in U.S. Pat. Nos.5,278,258 and U.S. Pat. No. 5,391,590 (Gerace et al). Generally lowtemperature curing at body temperature means a slow process and up to 12hours may be needed to complete their setting and their slow setting mayresult in material leakage out of the capsular bag through the surgicalincision. In order to overcome this problem, U.S. Pat. No. 4,542,542 andU.S. Pat. No. 4,608,050 (Wright et al) disclose such a silicon basedinjected system which is partially cured by heat in the vicinity of theinjection hole of the capsular bag to accomplish a first sealing effect.

[0005] Alternatively to thermocured silicone systems, photopolymerizablelens materials have been suggested which are activated after injectioninto the capsular by light in the presence of a photoinitiator. In thearticles by Hettlich et al in German J Ophthalmol (1992), Vol. 1, pages342-5 and 346-349, there are disclosures of how to employphotopolymerization of a monomer system injected into the capsular bagof the eye. An example of such an injectable system is also described inEP 414219, in which the liquid composition comprises a difunctionalacrylate and/or methacrylate ester and a photoinitiator capable of beingpolymerized by light of a wavelength range between 400-500 nm. Further,the International patent application PCT/EP99/04715 is directed to aninjectable photocurable aqueous solution of pre-polymerized units whichis capable of forming a lens implant with a suitable elasticity modulusafter final a crosslinking process triggered by visible light. Even ifsuitable polymerizable systems are at hand for preparing injectablelenses, there is still a considerable problem to obtain control of therefractive outcome of the eye after implantation. Accordingly, Hettlichet al suggested that by filling the capsular bag to varying degrees, oralternatively influencing the anterior or posterior capsular curvature,refractive control eventually would become possible.

[0006] O Nishi et al in Arch. Ophthalmol., 1997, Vol. 115, 507-510describe experiments with direct injection of silicone material into theemptied capsular bag in cadaver pig eyes with subsequent plugging of thecapsule and molding of the silicone into a synthetic lens. By using thisprocedure, the ability of the capsular bag to mold the injected siliconewas investigated. It was found that different values of accommodationamplitude could be accomplished dependent on if the implanted lens wasmolded with a zonal tension applied on the capsule compared to when saidtension was abolished. Nishi et al suggested that when (if) the eye isatropinized postoperatively, the lens capsule will conform to itsnon-accommodated state, which should yield the optimal amplitude ofaccommodation according to the investigated lens refilling principle. Inthe experiments referred to by HJ Hettlich in Accommodative LensRefilling Principles and Experiments© 1996 Pharmacia & Upjohn Groningen,the difficulties in obtaining the expected 30D myopic eye after lensinjection are acknowledged.

[0007] Although there has been a considerable progress in thedevelopment of materials and surgical techniques for injectable lenses,considerable efforts are still needed to control the refractive outcomeof this type of lenses. In particular, selection methods of suitablematerials and improved control of the lens forming process afterrefilling the capsule will be necessary to carefully predict therefractive outcome of the eye subjected to lens replacement.

DESCRIPTION OF THE INVENTION

[0008] It is an object of the present invention to provide for a methodof restoring the vision of an eye having an impaired lens to apredetermined refractive value of the eye by introducing a polymerizablefluid in the capsular bag

[0009] It is also an object of the present invention to provide for amethod wherein the refraction of the eye with the injected lens materialis controlled and compared with a predetermined refractive value of theeye and when necessary adjusted comply with said predetermined valuebefore finalizing the polymerization to the final lens implant.

[0010] It is a further object of the present invention to provide for amethod of selecting suitable polymerizable fluid to be introduced intothe capsular bag of the eye and subsequent polymerization into anintraocular lens.

[0011] It is a still further object of the invention to provide formethod to provide for a method, wherein the capsular bag of the eyefilled with a polymerizable fluid can be affected so as to vary andcontrol the refractive value of eye before polymerizing the fluid intothe final lens implant.

[0012] According to a first aspect, the present invention relates tomethod of pre-selecting a polymerizable fluid to be introduced into thecapsular bag and formed to an implanted replacement lens for an impairednatural lens. Typically, the natural lens to be replaced suffers fromcataract formation, but also presbyopic lenses, i.e. lenses havingcompletely or partially lost their capacity of accommodation, are alsoconceivable to be substitute within the context of the presentlyinvented methods. The polymerizable fluid is capable of being formedinto an intraocular lens by means of one ore several polymerizationreactions. The resulting lens is intended to provide the eye with adetermined desired refractive outcome value estimated as opticallysuitable or ideal for the individual elected to undergo surgery. Thepre-selection method comprises measuring of selected eye dimensionsincluding corneal curvature (anterior or posterior curves or both), theaxial length of the eye and the anterior chamber depth. The personskilled in this technology is knowledgeable of several measurementmethods to obtain this information and thereby finding relevantinformation about the eye, including the refractive value of the cornea.From these values the shape and the volume of capsular bag is estimatedand thereby it is possible to calculate the quantity and refractiveindex of the polymerizable fluid to be introduced in the capsular bag inorder to obtain a refractive value that sufficiently complies with thedesired refractive outcome value of the individual eye. Typically, suchcalculations comprise the determination of a lens model refractive value(the refractive value necessary for the lens to restore the vision) fromthe measured corneal refractive value and the desired refractive outcomevalue. By further estimating the shape and thereby the volume of theindividual capsular bag together with lens model refractive value, aquantity of polymerizable fluid with a specific refractive index isdetermined. According to one embodiment of the method, a polymerizablefluid then is selected from a kit of polymerizable fluids with a rangeof different refractive indices. In practical terms, the surgeon canselect the determined quantity of the fluid of the kit having arefractive index value, which is most compatible to the estimated valueof the refractive outcome value. Alternatively, a polymerizable fluidhaving an identical refractive index value to what has been estimatedcan be ordered from a manufacturer. Preferably, such kits ofpolymerizable fluids will have a range of refractive indices varyingfrom about 1.39 to about 1.6. As discussed in more detail below, severalsuitable polymerizable fluids are conceivable for the kit which complywith such requirements as being easy to inject with conventionalequipment, having suitably high specific gravity and providing optionsto obtain suitably high refractive indices and yet obtaining desirablemechanical characteristic for intraocular lenses after polymerization,including sufficiently low modulus to obtain an implanted lens, that canundergo accommodation when influenced by the ciliary muscles of the eye.The kit can typically comprise a range of such fluids filled inmulti-compartment containers, separately stored from agents necessary tobring about the polymerization. Advantageously, the multi-compartmentcontainers are provided with means to establish fluid communicationbetween the containers just prior to the administration into thecapsular bag and with means, either to inject the fluid, or to operateon the container with a conventional injection device. Many suchcontainers are known to the skilled person and will not be describedherein in more detail.

[0013] The present invention also pertains to a method of restoring thevision of an eye by removing an impaired lens from the capsular bag andreplacing said lens with a quantity of a polymerizable liquid with thepurpose of forming an intraocular lens with a predetermined refractiveoutcome. The defect natural lens is preferably removed by state of theart surgical interventions including eye opening with a small incision(about 1 mm), capsulotomy with capsulorhexis (about 1 mm) and lensectomy(removal of the natural lens) for example with phacoemulsification.Optional measures taken after finalizing the lensectomy can includeconventional methods to preserve the capsular integrity and preparingthe capsule, such as cleaning and anti-PCO treatment. The procedures ofsurgically removing the impaired lens are not parts of the presentinvention and will accordingly not be discussed in detail hereinafter.The inventive method comprises the determination of a desired refractiveoutcome value suitable for the eye, which is performed according tostandard optical procedures, which may have been performed at an earlieroccasion than the remaining steps of the method. Frequently, the desiredrefractive outcome of the patient is an emmetropic eye. The methodfurther comprises the steps of introducing the polymerizable solutioninto the capsular bag and thereafter determining the refractive value ofthe eye. This refractive value is then if necessary compared with thedesired refractive outcome value. The refractive value of the eye withthe polymerizable fluid introduced in the capsular bag is then adjustedto obtain a value that complies with said desired value of refraction.In this context complying values means that they at best completelycoincide with an accuracy relevant to the applied measuring means, orthat the values sufficiently conform to each other considering what isclinically applicable in the present case. Further in this context,adjusting the refractive value of the eye will mean that the lens systemof the capsular bag and polymerizable solution is affected, so as tobring about a sufficient change in eye refraction, such that saidrequested compliance is obtained. It is to be understood that thecomparison of the mentioned refractive values and the subsequentadjustment if necessary can be repeated one or several times in aniterative process, so as to approach sufficiently complying refractivevalues. In such a repetitive process, it is also to be understood thatdifferent measures to adjust the refraction can be considered in eachadjusting procedure. As will be explained below, the present inventionintroduces several alternatives to provide such adjustments by affectingthe mentioned provisional lens system and thereby obtaining refractivecontrol of the eye during the formation of the intraocular lens. Whensufficiently complying values are obtained, the formation of a lensimplant from the polymerizable liquid is initiated by starting apolymerization reaction from the constituents of the fluid. As a part ofthe formation process, it also intended that the polymerization can beperformed in one or several steps with intermediate control of therefraction of the eye and if necessary refraction adjustments can bemade in accordance with what has been described above. The refractivevalues of the eye as performed in the method after introducing thepolymerizable fluid in the capsular bag can be made with on-linerefractometry, for example as outlined in Journ. Cataract. Refract.Surg., 1989, Vol. 15, pp. 597-8.

[0014] According to a preferred embodiment, the polymerizable solutionis pre-selected in accordance with what has been described in theforegoing part. Alternatively, a polymerizable fluid can be directlyselected on the basis of other criteria.

[0015] When conducting the method it is also preferable to direct arinsing fluid into the anterior chamber of the eye. The rinsing fluid isconventionally employed during cataract surgery in the process oflensectomy by introducing a probe in the anterior chamber of the eye. Aswill be discussed later, the rinsing fluid can be employed in therefractive control of the eye during lens formation. In the presentmethod, the rinsing fluid is a saline solution provided with a specificrefractive index. It is preferable that the polymerizable fluid isintroduced in the capsular bag by means of injection, suitably throughthe orifice already created in the wall during the removal of theimpaired natural lens. For this purpose, it is a prerequisite that thepolymerizable fluid has a sufficiently low viscosity so it can beefficiently injected through a standard cannula with an 18 Gauge needleor finer. Preferably, the polymerizable fluid has a viscosity belowabout 60000 cSt and more preferably, below about 8000 cSt.

[0016] According to one aspect of the invention, the polymerizable fluidcomprises a polymerizable polysiloxane composition, suitably alsocomprising a crosslinking agent to participate in the polymerizingforming process, i.e. a crosslinking process. According to onealternative of this aspect, the polysiloxane composition furthercomprises a catalyst activated by heat to initiate the crosslinkingprocess. In another alternative, the polysiloxane composition comprisesa photoinitiator that suitably is activated by visible light, inparticular blue light. A useful polysiloxane composition can be found inthe International Patent Application PCT/EP99/07780 that describessilicone compositions adapted for being thermocured in the capsular bagwith a suitable high density above 1.0 g/cm³. The polymerization afterinjection such a composition can be initiated by raising the temperatureof the rinsing fluid to a value necessary to activate the catalystdriven polymerization. Typically, such a increase in temperature can befrom about 20 to about 40° C. Alternatively, it is conceivable to usethe photocurable compositions designed for intraocular lens productiondirectly in the capsular bag of the eye, as described in theInternational Patent Application PCT/EP99/04715. From the teachings ofthese documents, the skilled person can readily obtain a wide range ofpolymerizable polysiloxane compositions suitable for injection into thecapsular bag, having a range of different refractive indices varyingfrom about 1.39 up to 1.6, as is suitable for the above-mentioned kitfor selecting an appropriate polymerizable fluid. Both these documents,which herewith are incorporated as references in their entirety, providepolysiloxanes designed for injection into the capsular bag which by aspecific selection of substituents on the polysiloxane backbone enablessuitable variation range in refractive index, while still retainingcharacteristics of sufficiently high density (preferably higher thanabout 1.0 g/cm³) and excellent mechanical characteristics for lensproduction.

[0017] According to an alternative aspect, the polymerizable fluidcomprises an aqueous composition of a hydrophilic polymer carrying sitesfor crosslinking, wherein said aqueous composition further comprises acrosslinker. Preferably, the formation of a lens implant is initiated byactivating a photoinitiator by irradiation of a predetermined wavelengthor range of wavelengths. Most suitable in the context of the presentmethod is to select a photoinitiator activated by visible light,preferably blue light. Examples of such compositions are found in theInternational Patent Application published as WO 99/47185, whereincrosslinkable hydrophilic units of different polymers are disclosed.

[0018] As earlier mentioned, it is an important part of the inventivemethod to be able to control the refraction of the eye, by performingrefraction adjustments of the system consisting of the capsular bagcontaining the polymerizable fluid.

[0019] According to one embodiment the refractive value of the eye isadjusted by changing the pressure exerted on the capsular bag. Apressure change will result in that shape of the capsular bag is alteredand thereby the curvature of its refractive surfaces. Varying thepressure exerted on the capsular bag is preferably performed by alteringthe pressure of the rinsing fluid as introduced in the anterior chamberof the eye with probe in fluid connection with a supply container.Accordingly, the fluid pressure of the rinsing liquid can convenientlybe controlled by heightening or lowering the supply container ascorrelated to scale of height and pressure (mm Hg). The flowing rinsingfluid can thereby directly be used to exert different and readilycontrollable pressures on the anterior side of the capsular bag andthereby model its overall shape and its refractive value.

[0020] According to another embodiment, the refractive value of the eyeis adjusted by affecting the state of accommodation and therebyobtaining control of the shape of the capsular bag. In a moreaccommodated state, the capsular bag with the fluid lens material ismore rounded, whereas a less accommodated state of the lens results in amore flattened shape of the capsular bag. The different states ofaccommodation are caused by stretching and relaxation of the capsularbag by zonulas as influenced by the contraction and relaxation of theciliary muscles. Several alternatives are conceivable to affect thestate of accommodation. One alternative is either local or systemicadministration of drugs, which influence the state of the ciliarymuscles, such as pilocarpine. Another alternative to affect the state ofaccommodation is to visually stimulate the fellow eye not elected tosurgery. The inadvertent accommodation following in the eye subjected tosurgical intervention can thereby used for refractive adjustment.

[0021] According to a further embodiment, the refractive value of theeye is adjusted by changing the pressure inside the capsular bag.Suitably, such an adjustment is accomplished by changing the volume ofthe polymerizable solution. The volume can be adjusted either byre-introducing or withdrawing fluid from the capsular bag. Preferably,this is performed by means of an injection device through the previousinjection site. It is also conceivable to accomplish changes in thefluid volume by letting the fluid swell or shrink in a controlledmanner. It is to be understood that the different embodiments ofadjusting the refraction can be combined in various manners. Whenconducting the inventive method, the surgeon will have the possibilityto employ one way of affecting the capsular shape, thereaftercontrolling the refractive value, and if necessary for complying withthe predetermined value use another embodiment of adjusting therefraction.

[0022] When starting the formation of the lens implant, a polymerizingprocess is initiated in the capsular bag by physically affecting thepolymerizing fluid which can be accomplished in different mannersdependent on what polymerizable fluid system that has been selected inaccordance with the earlier discussions. According to one embodiment ofthe invention the polymerization is initiated by the influence of heat.The heating of the fluid can be generated by different means, such asirradiating the capsule with infrared radiation or by increasing thetemperature of the rinsing liquid, as earlier mentioned. According to adifferent embodiment, the polymerization process can be initiatedsubstantially instantaneously by means of irradiation, preferably bymeans of exposing the eye to visible light, in particular to blue light.

[0023] The step of forming a lens implant can also involve a partialpolymerization the polymerizable fluid, before final polymerization. Insuch case, refractive value can be controlled after finalizing a partialpolymerization and compared with the predetermined value. If thesevalues do not comply sufficiently, one or several of the mentionedadjustment steps can be performed until the refractive value of the eyeagrees with the desired predetermined value. Indeed several partialpolymerization processes are conceivable, each with a subsequentrefraction control and optional adjustment. The partial polymerizationpreferably applies to a local polymerization of the fluid, even ifselective partial polymerization into a homogenous semi-solid fluid isconsidered to be a part of this embodiment. The local polymerization canbe accomplished by heating the capsular at a selected part, for exampleby directed infrared radiation. Alternatively, heated rinsing liquid canbe directed to a region or site of the capsular bag for a timesufficient to complete a local polymerization process. For example,local polymerization can be employed to obtain a first sealing effect ofthe fluid filled capsular bag. For this purpose, a thin sealingshell-like solid part around the inner periphery of the capsular bag canbe obtained by directing heated rinsing liquid for a suitable timearound its outer periphery. A local polymerization around the opening orinjection site can also be obtained, for example by polymerizing aroundthe injection needle immediately after introducing the liquid into thecapsular bag. By effectively sealing the capsular bag, it is possible tomore safely conduct necessary adjustments without risking that theliquid leaks out of the injection site. Partial and localpolymerization, as outlined above, can also be obtained by irradiationwith suitable light, for example by focussing the light to the desiredsite. After conducting the step or steps of partial polymerizationperforming refraction control of the eye, the lens forming process iscontinued by a final polymerization. This final curing step will resultin the permanent intraocular lens which now will provide the eye withrefractive value complying with the predetermined value and a restoredvision. It is obvious necessity that the refractive value of the eyeshall be kept constant, i.e. the shape of the capsular bag, during thisfinal polymerization or during the entire formation step if no partialpolymerization is conducted.

[0024] The present invention obviously also provides for an advantageousmethod of controlling the refractive value of the eye during ophthalmicsurgery when the natural lens is replaced in the capsular bag by apolymerizable fluid. The control is exerted by the mentionedalternatives to modify the shape of the capsular bag into which apolymerizable fluid has been introduced.

[0025] Consequently the present invention admits that the patient isprovided with an intraocular lens with an accurately determinedrefractive value that can restore the vision to a predetermined value.This is a considerable advantage when compared to conventional surgerywith stiff or foldable lenses no refractive adjustments can be performedonce the lens is inserted into the capsular bag. In combination with thefact that the present invnetion permits a surgical intervention causingless trauma from large incisions in the eye, it is obvious that highlyadvantageous contributions to the art are provided.

DETAILED AND EXEMPLIFYING DESCRIPTION OF THE INVENTION

[0026] The inventive methods directed to refilling the natural humanlens capsule with a polymerizable fluid are directed to securing thatthe intended post-operative refraction is achieved. One way is to adjustthe lens power during the operation. Another way is to predict theamount of fluid and the refractive index of the fluid pre-operatively,which guarantee a correct post-op refraction. Within the context of thepresent invention it also possible to combine both methods. In such acase, the appropriate volume and refractive index of the polymerizablefluid are determined prior to the surgical procedure, then during theoperation, the refraction is further fine-tuned to the intended value.When the human lens is impaired, for instance by cataract or presbyopia,the impaired lens can be removed out of the lens capsule. Thereafter apolymerizable fluid can be injected into the capsule and polymerized.The new lens is molded by the capsule. The newly molded lens must havethe correct lens power in order to give the patient the intendedpostoperative refraction. The lens power depends largely on the amountof injected fluid and the refractive index of the fluid. This means thatthe lens power can be controlled by these two parameters. Based on thepredictions of the volume and refractive index for a specific patient,the surgeon can be provided a kit of materials at the operating table,from which he select the right one for the specific patient.

[0027] In the following example, a method is described which predictsthe volume and refractive index of the polymerizable fluid, based onmeasurements on the individual patients and combined with data for theaverage human eye.

EXAMPLE 1

[0028] The determination is based on the combination of two sets ofdata:

[0029] 1. General data of the human eye, measured on a representativepopulation

[0030] 2. Measurements of the individual patient

[0031] 1. General Data

[0032] Lens Thickness

[0033] The lens thickness is very much depending on age. Within an agegroup, the spread in lens thickness is very small. Shum, Ko, Ng and Lin(1993) measured the lens thickness of a group of 76 subjects ofvirtually the same age (s.d. 1.2 month). On an average lens thickness of3.49 mm he found a standard deviation of 0.02 mm, which is 0.5%. The agerelation of the lens thickness is best described by Koretz, Kaufinan,Neider and Goeckner (1989), who found a relation of

LT=3.220+0.021*A  (1)

[0034] LT=lens thickness [mm]

[0035] A=age [y]

[0036] When using this relation, the actual input for the calculation isage, and not lens thickness.

[0037] Relation between Anterior and Posterior Lens Radius

[0038] The actual lens radii of an individual patient may differ a lot,however there is always a certain relation between the two. Based onmeasurements on human cadaver eyes, Glasser & Campbell (1999) found therelation of:

Rp=−0.261*Ra−2.631  (2)

[0039] Rp=posterior radius [mm]

[0040] Ra=anterior radius [mm]

[0041] Relation between Lens Equatorial Diameter and Lens Focal Length

[0042] The lens equatorial diameter is hidden behind the iris. It cannot be measured with the equipment that is normally available in theophthalmic practice. Therefor a reasonable estimate can be made, usingthe relation that was found by Glasser & Campbell (1999), based onmeasurements on human cadaver eyes:

LD=0.0502*FL+5.288  (3)

[0043] LD=lens equatorial diameter

[0044] FL=lens focal length

[0045] Relation between the Natural Lens Focal Length and the RefilledLens Focal Length

[0046] The lens capsule and the lens do not need to have the same shape.As a result it is possible that after refilling the lens, the shape ofthe lens has changed. This was seen in calculations of lens refilling.This phenomenon also follows from the results of Glasser & Campbell(1999): For most lenses the focal length changes after decapsulation ofthe lens. However, this effect disappears at the age of 60 years, whichcorresponds to the age of full presbyopia. From this it can be concludedthat the focal length of the refilled lens will be equal to the focallength of the original lens, provided that the refill material has therefractive index of natural lens material.

[0047] Measurements on the Individual Patient

[0048] Keratometer

[0049] With the keratometer, the corneal power is measured. This iscurrently a standard measurement in cataract surgery. Alternatively, thecorneal curvature (radius) can be measured. The relation between cornealcurvature and corneal power is:

K=337.5/Rc  (4)

[0050] K=Corneal power [D]

[0051] Rc=Curvature radius of the cornea

[0052] A-Scan

[0053] With an A-scan, the axial dimensions of the eye can be measured.Also this is currently standard practice in cataract surgery. Ingeneral, it results in a measure of the anterior chamber depth and thetotal axial length of the eye.

[0054] Refraction and Refraction History

[0055] The refraction is measured by the optometrist. When the patientis currently blind, the refraction can not be measured. In such a casethere are two alternatives:

[0056] 1. The refraction history of the patients eye, during the periodthat the patient was not blind.

[0057] 2. The refraction and/or the refraction history of the patient'sfellow eye.

[0058] Calculation Scheme

[0059] 1. Determination of the lens thickness, from the age of thepatient

[0060] 2. Determining the radii of the lens, based on the known opticalsurfaces and refraction of the eye.

[0061] 3. Determining the focal length of the natural lens

[0062] 4. Determining the lens equatorial diameter, based on the lensfocal length

[0063] 5. Determining the volume of the natural lens.

[0064] 6. Based on the desired post-op refractive outcome, select theappropriate refractive index.

[0065] The volume to be used is equal to the volume of the natural lens.The refractive index of the material is adapted, so that thepredetermined refractive outcome for the patient will be reached.

[0066] Patient Data:

[0067] Age: 63 year Results of the ophthalmic exam: Keratometer reading:43.7 Diopter A-scan: Axial length 23.35 mm Anterior chamber depth 3.25mm Historic refraction: +2.5 Diopter spherical equivalent (stable).

[0068] Accordingly, the calculations according to the calculation schemeis:

[0069] 1. According equation (1), the lens thickness is 4.543 mm.

[0070] 2. According equation (4), the cornea has a radius of 7.723 mm.

[0071] The length of the vitreous is the axial length, minus theanterior chamber depth and minus the lens thickness. So far the opticalsystem is: Refractive Surface Name Radius Thickness index 1 Cornea+7.723 3.25 1.3375 2 Lens Ra 4.543 1.422 3 Vitreous Rp 15.557 1.336 4Retina — — —

[0072] Since, according equation (2), Rp is a function of Ra, there isonly one variable in this system. This variable can be solved, using thecondition that it has to result in the known or historic refraction.Here a paraxial ray tracing procedure is used, adapted from thespreadsheet that is used to calculate A-constants for IOL's. Thisresults in the lens radii:

[0073] (Refraction Rx=spectacle refraction. For modeling the eye, thespectacle is made of Crown glass (Agarwal's principles of Optics andRefraction), 2 mm thick, with it's anterior surface 14 mm in front ofthe cornea).

[0074] Ra=12.286 mm

[0075] Rp=−5.838

[0076] 3. The focal length of the natural lens is determined by thedimensions and refractive index:

[0077] Ra=12.286 mm

[0078] R_(p)=5.838 mm

[0079] Thickness=4.543

[0080] Refractive index=1.422

[0081]

Lens power (P), according the thick lens equation is 21.40 diopter andthe focal length is 1336/P=62.425 mm.

[0082] 4. Equatorial diameter, according equation (3) is 8.422 mm.

[0083] 5. The volume of the lens, based on an ellipsoid, with the knownthickness and equatorial diameter is 186.7 mm³. according the thick lensequation is 21.40 diopter and the

[0084] The volume of an ellipsoid is: V={fraction (4/3)}*π*a²*b

[0085] With :

[0086] a=diameter/2

[0087]  b=thickness/2

[0088] 6. The refractive index can now be chosen for a specificpost-operative refractive outcome. An index of b 1.422 will result inthe pre-op (historic) refraction of 2.5 diopter. The result of differentrefractive indices can be calculated by paraxial ray tracing, andresults in the following table (Rx=post-op refraction): Rx η −3 1.457 −21.451 −1 1.445 0 1.439 1 1.432 2 1.426 2.5 1.422 3 1.418 4 1.411 5 1.4036 1.395

REFERENCES

[0089] Agarwal, L. P. (1998). Agarwal's Principles of Optics andRefraction (5 ed.). New Dehli: CBS Publishers & Distributers.

[0090] Glasser, A., & Campbell, M. C. W. (1999). Biometric, optical andphysical changes in the isolated human crystalline lens with age inrelation to presbyopia. Vision Research, 39(11), 1991-2015.

[0091] Koretz, J. F., Kaufman, P. L., Neider, M. W., & Goeckner, P. A.(1989). Accommodation and presbyopia in the human eye—aging of theanterior segment. Vision Res, 29(12), 1685-1692.

[0092] Shum, P. J., Ko, L. S., Ng, C. L., & Lin, S. L. (1993). Abiometric study of ocular changes during accommodation (see comments).Am J Ophthalmol, 115(1), 76-81.

1. A method of pre-selecting a polymerizable fluid capable of being formed into an intraocular lens implant after being introduced into the capsular bag of the eye from which an impaired natural lens has been surgically removed, comprising the steps of: (a) determining a desired refractive outcome value suitable for the eye; (b) measuring one or several eye dimensions selected from corneal curvature, axial length of the eye or anterior chamber depth; (c) estimating the shape of the capsular bag; (d) calculating the quantity and the refractive index of the polymerizable fluid to be introduced in the capsular bag for obtaining a refractive value that sufficiently complies with the desired refractive outcome of (a);
 2. A method according to claim 1, comprising determining a lens model refractive value from a corneal refractive value obtained from step (b) and the desired refractive outcome value (a).
 3. A method according to claim 2, comprising obtaining the quantity and refractive index of the polymerizable fluid from the lens model refractive value and the estimations in step (c).
 4. A method according to claim 1, comprising selecting a polymerizable fluid, having the most compatible value to that obtained in step (d), from a kit of polymerizable fluids having a range of refractive indices.
 5. A method according to claim 4, wherein said kit has a range fluids having refractive indices varying from about 1.41 to about 1.6.
 6. A method according to claim 5, wherein said kit comprises a range of fluids filled in multi-compartment containers separately stored from agents necessary to bring about the polymerization.
 7. A method according to claim 6, wherein fluid communication can be established between said compartments just prior to the fluid administration to the capsular bag.
 8. A method of restoring the vision of an eye by removing an impaired lens from the capsular bag and replacing said lens with a quantity of a polymerizable liquid comprising the consecutive steps of: (a) determining a desired refractive outcome value suitable for the eye; (b) introducing the polymerizable solution into the capsular bag; (c) determining the refractive value of the eye; (d) comparing the refractive values of steps (a) and (c); (e) adjusting the refractive value of the eye to comply with the value obtained in step (a); (f) forming a lens implant from the polymerizable liquid providing the eye substantially with the refractive value determined in step (a).
 9. A method according to claim 8, wherein the polymerizable solution is pre-selected in accordance with any of claims 1 to
 7. 10. A method according to claim 8, wherein rinsing fluid is directed into the anterior chamber of the eye.
 11. A method according to claim 8, wherein the polymerizable solution is introduced into the capsular bag by means of injection.
 12. A method according to claim 11, wherein the polymerizable fluid has a sufficiently low viscosity so as to be capable of being injected through a standard cannula with an 18 Gauge needle or finer.
 13. A method according to claim 12, wherein the polymerizable fluid has a viscosity below about 60000 cSt.
 14. A method according to claim 8, wherein the polymerizable fluid comprises a polysiloxane composition.
 15. A method according to claim 14, wherein said polysiloxane composition further comprises a crosslinking agent.
 16. A method according to claim 19, wherein said polysiloxane composition further comprises a catalyst activated by heat.
 17. A method according to claim 14, wherein said polysiloxane composition comprises a photoinitiator.
 18. A method according to claim 16, wherein said photoinitiator is activated by visible light, preferably blue light.
 19. A method according to claim 8, wherein said polymerizable fluid comprises an aqueous composition of a hydrophilic polymer carrying sites for crosslinking.
 20. A method according to claim 19, wherein said aqueous composition comprises a crosslinker
 21. A method according to claim 20, wherein said aqueous composition comprises a photoinitiator activated by visible light.
 22. A method according to claim 8, characterized by adjusting the refractive value by changing the pressure exerted on the capsular bag.
 23. A method according to claims 10 and 22, characterized by changing the pressure of the rinsing liquid.
 24. A method according to claim 8, characterized by adjusting the refractive value by affecting the state of accommodation of the eye.
 25. A method according to claim 24, characterized by affecting the state of accommodation by administering drugs influencing the ciliary muscle.
 26. A method according to claim 24, characterized by affecting the state of accommodation by visually stimulating the fellow eye.
 27. A method according to claim 8, characterized by adjusting the refractive value by changing the pressure inside the capsular bag.
 28. A method according to claim 27, characterized by changing the volume of the polymerizable solution.
 29. A method according to claim 8, wherein the step of forming a lens implant involves polymerization under the influence of heat.
 30. A method according to claim 27, characterized by increasing the temperature of the rinsing fluid.
 31. A method according to claim 29 characterized by directing infrared radiation to the capsular bag.
 32. A method according to claim 8, wherein the step of forming a lens implant involves polymerization initiated by irradiation.
 33. A method according to claim 32, wherein the irradiation comprises visible light, preferably blue light.
 34. A method according to claim 8, wherein the step of forming a lens implant involves partially polymerizing the polymerizable fluid, before final polymerization
 35. A method according to claim 34, comprising a partial polymerization and subsequently repeating steps (c) and (d), before optionally adjusting the refractive value to comply with the value obtained is step (a) before final polymerization.
 36. A method according to claim 34, comprising locally polymerizing the polymerizable fluid by heat.
 37. A method according to claim 36, comprising directing heated rinsing liquid to a region of the capsular bag for a time sufficient to accomplish local polymerization.
 38. A method according to claim 35, comprising directing heated rinsing liquid around the periphery of the capsular bag.
 39. A method according to claim 35, comprising directing heated rinsing liquid to a site of the capsular bag to accomplish a sealing effect.
 40. A method according to claim 35 comprising directing infrared radiation to the capsular bag.
 41. A method according to claim 8, wherein the forming of the lens implant is conducted when the eye is the unaccommodated state.
 42. A method of controlling the refractive value of the eye during ophthalmic surgery when the natural lens is replaced in the capsular bag by a polymerizable fluid capable of being polymerized into lens implant, thereby providing the eye with restored a vision complying with a predetermined refractive value of the eye, characterized by modifying the shape of the capsular bag containing the polymerizable fluid.
 43. A method according to claim 42 characterized by changing the pressure exerted on the capsular bag.
 44. A method according to claim 42, characterized by changing the pressure of the rinsing liquid.
 45. A method according to claim 42, characterized by affecting the state of accommodation of the eye.
 46. A method according to claim 45, characterized by affecting the state of accommodation by administering drugs influencing the ciliary muscle.
 47. A method according to claim 46, characterized by affecting the state of accommodation by visually stimulating the fellow eye.
 48. A method according to claim 42, characterized by changing the pressure inside the capsular bag.
 49. A method according to claim 48, characterized by changing the volume of the polymerizable solution.
 50. A method of restoring the vision of the eye to a predetermined refractive value characterized by introducing a polymerizable solution into the capsular bag of eye, from which the natural lens has been removed and thereafter polymerizing said solution into an intraocular lens implant which provides the eye with a refractive value sufficiently complying with said predetermined value.
 51. A method according to claim 50, wherein the polymerizable solution is selected in accordance with any of claims 1 to
 7. 52. A method according to claim 50 or 51, further comprising controlling the refractive value of the eye before polymerizing the solution into the intraocular lens.
 53. A method according to claim 52, further comprising comparing the refractive value obtained by the control with the predetermined refractive value.
 54. A method according to claim 53, further comprising adjusting the refractive value to sufficiently comply with the predetermined refractive value.
 55. A method according to claim 54, wherein the refractive value is adjusted by modifying the shape of the capsular bag.
 56. A method according to claim 55 characterized by adjusting the refractive value by changing the pressure exerted on the capsular bag.
 57. A method according to claim 55 characterized by changing the pressure of the rinsing liquid.
 58. A method according to claim 56, characterized by affecting the state of accommodation of the eye.
 59. A method according to claim 58, characterized by affecting the state of accommodation by administering drugs influencing the ciliary muscle.
 60. A method according to claim 58 characterized by affecting the state of accommodation by visually stimulating the fellow eye. 